Lower delta plain interdistributary deposits — An example from the Westphalian of the Lancashire Coalfield,northwest England

A large quarry at Billinge Beacon in Lancashire, northwest England, has provided an excellent exposure of part of the Lower Westphalian A (Upper Carboniferous) Coal Measures sequence which was deposited in a lower delta plain setting. The main horizon exposed, known as the Dyneley Knoll Flags, is interpreted as the proximal reaches of two crevasse-initiated minor delta complexes, into the lower of which has been incised a sinuous minor distributary channel. The channel, which was approximately 120 m wide, built a 160 m wide channel belt by limited lateral accretion with time; vertical accretion appears to have been the dominant infilling mechanism. This produced a stacked series of epsilon cross-strata, made up of rhythmically interbedded sandstone and silty claystone. The peculiar style of infilling of the channel is ascribed to deep incision of the channel into minor delta deposits, and possibly the influence of a seasonal climate.